Gap junctions formed by connexin 43 (Cx43) play an important role in transmitting signals between bone cells essential for bone formation and remodeling. Osteocytes express large amounts of Cx43 compared with other bone cell types; however, they only form gap junctions with other osteocytes through the tips of their dendritic processes. Our preliminary data suggests that in addition to gap junctions, primary osteocytes and osteocyte-1 like MLO-Y4 cells express functional Cx43-forming hemichannels and these hemichannels mediate the immediate response of osteocytes to mechanical stress. The central hypothesis is that hemichannels formed by Cx43 have essential, yet distinct functions from gap junctions in the regulation of the osteocytic response to mechanical strain, and a5-integrin regulates the opening of hemichannels. Two specific aims will be pursued: 1) Identify the essential roles that Cx43-forming hemichannels play in osteocyte responses to mechanical stress; 2) Determine if a5 integrin regulates the opening of hemichannels induced by fluid flow shear stress. The innovative and significant aspects of this proposal are the discovery of novel mechanisms for unconventional roles of Cx43-forming hemichannels in regulating osteocyte response to mechanical strain. This study will provide comprehensive training using biochemical, molecular, and functional techniques combined with unique mechanical engineering applications. [unreadable] [unreadable]